A Stable Downward Continuation of Potential Field Data: A Case of Study of the Kalatag Polymetallic District, NW China

Downward continuation is a useful tool for improving the resolution of potential field data. It reconstructs the field at a lower observation height from the observed field to highlight detailed anomalies of the field source distribution and to distinguish overlapping anomalies of multiple targets. However, downward continuation is unstable and sensitive to noise in the data; thus, influencing the popularity of this method. Here, we present an iterative filtering method in wavenumber domain based on improved Gaussian function to accomplish downward continuation of potential field data. In this method, multiple corrections are implemented on the continuing plane by downward continuing the difference between the observed and the calculated field data to compensate for the precision of the downward continuation. The wavenumber responses of downward continuation operators of the proposed filter function were analyzed, and the performance and stability of the method were tested on a synthetic model. Satisfactory results were obtained, as the method yielded more accurate anomaly amplitude and demarcated boundary of field sources in the model as compared with other downward continuation methods. In addition, the technique was implemented on aeromagnetic data acquired from the Kalatag polymetallic district, NW China, and we further verified that the proposed method has stable convergence, which revealed accurately the shallow magnetic source features in this district.